Now that I have got over the whole disappointment with the @me.com address for push mail I am back to my two Google accounts (Google Apps with my corporate domain and regular Gmail) and I have sync'd my MobileMe but turned off the Mail functionality in the iPhone System prefs so it just does my calendars and contacts. Interestingly the very fact that you can individually select which parts of the MobileMe platform to use (Mail, calendars or contacts) suggests perhaps that they knew that it was going to be used for other mail accounts.
And with a combination of Spanning Sync on my Mac sending my multiple Gmail calendars to iCal and backwards I actually get a pretty good Gmail to iPhone sync albeit with the caveat that I have to at least open my computer to get Spanning Sync to activate and do the last leg.
Anyway, this is a lot more convoluted than I had hoped and it isn't "Exchange for the rest of us" as SJ suggested and so I am on the hunt for new and better methods.
So, an old fashioned doff of the cap to the quiet talent of the man who brought you Hardware Growler (still one of the only 5 or 6 apps bundled with every download of the great growl platform) and the flashes of wit and insight on his blog at Monkeyfood.com - the great Diggory. He led me to Nueva and its Exchange solution to push mail, calendars and contacts from Gmail. The article he put me onto is here, care of Beau Giles.
Thanks all. Any other workarounds appreciated.